EP0210588A2

EP0210588A2 - Antitumor polypeptide and a method of preparing the same

Info

Publication number: EP0210588A2
Application number: EP86110139A
Authority: EP
Inventors: Gen-Ichiro Soma; Den'ichi Mizuno; Hiroshi Shibai
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-07-29
Filing date: 1986-07-23
Publication date: 1987-02-04
Anticipated expiration: 2006-07-23
Also published as: EP0210588B1; DE3687246D1; DE3687246T2; EP0210588A3; JPH064675B2; JPS6226226A; ATE83246T1

Abstract

This invention relates to a novel anti-tumor polypeptide prepared by suspended-culture of human acute monocytic leukemia cells THP-1 under or after contact with a differentiation inducing agent. The novel anti-tumor polypeptide do not exhibit cytotoxicity against human normal cells but give cytotoxicity to human tumor cells Hela, KB and T-24 cells which is known to be insensitive to conventional TNF, and mouse tumor cells such as sarcoma 180 and L-1210. The antitumor polypeptides may be prepared by a non-expensive serum-free medium.

Description

Background of the Invention

(a) Fileld of the Invention

This invention relates generally to a novel antitumor polypeptide and, more specifically, to a novel human-derived antitumor polypeptide, generally classified into tumor necrosis factor (TNF), having selective toxicity against tumor - (transformed, neoplastic) cells.

(b) Description of the Prior Art

As a human-derived antitumor polypeptide having a cytotoxicity against mouse L-929 fibroblast cells, there is known a polypeptide, called TNF, which is obtained from a human cell line H-60 - (ATCC240) and the amino acid sequence of which is almost entirely determined [The Journal of Biological Chemistry 260, 2345-2354 (1985)].
Such a TNF polypeptide is known to be produced by Escherichia coli transformed with a recombinant plasmid [Nature 312 , 724-729 (1984, Dec. 20/27); Nature 313, 803-806 (1985, Feb. 28); Science 228, 149-154 (1985, Apr.12)]. The polypeptides produced by transformed Escherichia coli are identical with TNF disclosed in the above- ·described article, The Journal of Biological Chemistry 260 , when deduced from the base sequence of the cloned DNA, with the exception that TNF disclosed in Nature 313 lacks the two N-terminal amino acids, i.e., Val and Arg.

Summary of the Invention

The present invention contemplates the provision of the novel antitumor polypeptide having excellent activities and a method of preparing the same.
The present inventors have obtained a novel antitumor polypeptide from differentiation inducing agent-containing culture, especially suspended culture, of human acute monocytic leukemia cells THP-1 [Int. J. Cancer 26, 171-176 (1980)] which is quite different from the above-described HL-60 human cell line.

Brief Description of the Drawing

Fig. 1 is a graph showing the NaCI concentration capable of eluting the anti-tumor activity, when an anti-tumor polypeptide-containing mixture obtained from THP-1 cells in Example 1(1) is purified with the second FPLC. And the eluate is monitored for absorbance at 280 nm and for cytotoxic activity;
Fig. 2 is reverse phase FPLC elution pattern of TNF-1 with a linear gradient of acetonitrile;

Description of the preferred embodiment(s)

In accordance with the first aspect of the present invention there is provided an antitumor polypeptide containing a peptide fraction having the following N-terminal amino acid sequence:
Val-A-Ser-X-Thr-B-Thr-C-D-E-F-G-Val-Ala-His-Val-Ala-Asn
wherein A represents Arg or Lys, B represents Arg or Pro, C represents Arg or Pro, D represents Ser or Lys, E represents Arg or Pro, F represents Lys or Val, G represents Phe or Pro and X is an unidentified amino acid, and tryptic peptide fragments of

(1)Val-Val-Ala-Asn-Pro-Gln-Ala-Glu-Gly-Gln-Leu-Gln,
(2)Ala-Asn-Ala-Leu-Leu-Ala,
(3)Asn-GIn-Leu-Val-Val-X-X-X-Gly-Leu,
(4)lle-Ala-Val-X-Tyr,
(5)Val-Asn-Leu-Leu,
(6)Glu-Thr-Pro-Glu-Gly-ALa-Glu-Ala,
(7)Tyr-Glu-Pro-Ile-Tyr-Leu-Gly-Gly-X-phe and
(8)Leu-Ser-Ala-Glu-Ile-Asn-Arg-Pro-Asp-Tyr-Leu-Asp-Phe-Ala-Glu-Ser-Gly-Gln-Val-Tyr and having the following physical and chemical properties:
- (a) molecular weight : 17400+500 (SDS electrophoresis);
- (b) isoelectric point; pi 5.7+0.2 (isoelectric focusing gel electro-phoresis);
- (c) pH stability: stable at pH in the range of 6-9 ;
- (d) heat stability: activity is lost by about 60-70% when heated at 65°C, pH 7.0 for 1 hour;
- (e) stability to protease: inactivated;
- (f) physiological activity: shows no cytotoxicity against human normal cells but exhibits cytotoxicity against human transformed cells.

The above polypeptide may be produced, for example, by culture, preferably suspended culture, in a culture medium of human acute monocytic leukemia cells THP-1 [Int. J. Cancer 26m 171-176 (1980)1 under or after contacting them with differentiation inducing agents.
The differentiation inducting agent is a substance capable of inducing malignant monocyte cells into macrophages, granuloccyte cells. Examples of the differenciation inducing agents include hemin, actionomycin D, hexamethylene-aclacino mycin A, Teleocidin, mitomycin C, Bleomycin, propionic acid, sodium acetate, cadaverine, Tunicamycin, 12-o-tetradecanoyl-phrbol-13-acetate (TPA), lymphokines such as y-interferon, D-factor, arginase, histone Hi, lipopolysaccharide (LPS), lipid A, glucocorticoid, Id-25-dehydrooxyvitamin D3, poly(I), poly(ADP-ribose), BCG and chloroquine.
The contact of the human acute monocytic leukemia cells THP-1 with the differentiation inducing agent can be effected by culture, especially suspended culture, the THP-1 cells in a culture medium. The antitumor polypeptide may be produced by culture of THP-1 cells in the continual presence of the differentiation inducing agent. After the contact of the THP-1 cells with the differentiation inducing agent, however, the cells may be transferred to another culture medium containing no such inducing agent. In the latter case, an extracellular stimulating agent may be added to the medium to which the THP-1 cells have been transferred.
The stimulating agent is a substance which serves to change the cell walls or lysozome of for faciliating the discharge or ooze of endocellular macromolecules from the cells. Illustrative of suitable stimulating agents are lipopolysaccharides, lecthins and vitamin A.
The culture medium in which the THP-1 cells are cultured may be any conventional medium for culture of various animal cells. Rosewell Park Memorial Institute-1640 Medium (hereinafter referred to as RPMI-1640) is a suitable example of such a culture medium. Othermedia such as Dulbeccos Modified Eagle's medium, Eagle's minimum essential medium (hereinafter referred to as MEM medium) and Click medium may also be used. While the medium may be added with fetal bovine serum (hereinafter referred to as FBS), neonate bovine serum or horse serum, the use of serum-free medium generally gives extremely good results in the separation and purification of the antitumor polypeptide.
The suspended culture of the THP-1 cells is generally performed with a cell density of 1-5 x 10⁶/ml at 35-38°C under a carbon dioxide gas stream at concentration of 4-6 %.
The differenciation inducing agent is generally added to the medium at the commencement of the culture. The extracellular stimulating agent may be added to the medium either at the commencement of the culture or when the cells are grown to a significant degree. However, the antitumor polypeptide may be sufficiently produced without the addition of the stimulating agent. Rather, it is advantageous not to use the stimulating agent because of the convenience in the purification of the antitumor polypeptide.
The antitumor polypeptide obtained by the suspended culture of THP-1 cells may be quantitatively and qualitatively analyzed in the following manner. Target cells, L-929 cells [Proc. Natl. Acad. Sci. U.S.A. 72, 3666-3670] are grown in Eagle's minimum essential medium (MEM) added with 5% fetal bovine serum until 8x10' cells are contained per 100 µl of the medium and cultured on a flat bottom plate with 96 wells under conventional culturing conditions, namely at 37°C for 2 hours under 5% C0₂ and 100% H₂O. Then, actinomycin D is added to the medium until a concentration of 1 ag/ml is reached while adjusting the amount of the culture liquid to 150 µl. this is then immediately added with 50 µl of the sample diluted with MEM. The degree of the dilution is controlled adequately to determine ED50. The L-929 cell, the volume of which becomes 200 µl, is then cultured under the same conditions as above for 18 hours. For the purpose of measuring the cell necrosis activity, the entire medium is removed and 2% methyl alcohol solution containing 0.2% crystal violet is added for fixation staining. Since the karyote cells are stained but the cells killed and freed from the bottom of the flask are not stained with the crystal violet, the cell necrosis activitiy may be directly measured. Thus, the color density is measured as an absorbance of OD 590 nm and compared with that of the control. The activity is expressed as unit activity per 1 ml of the sample and is defined as the degree of dilution of the sample with which 50% of the L-929 cells are alive. For example, a sample diluted with one volume of a diluent and providing ED50 is defined as having an activity of 1 unit/mi.
The polypeptide thus accumulated in the culture is purified by conventional protein purification techniques such as ion exchange chromatography using a basic anion exchanger, salting out, dialysis, gel filtration, hydrophobic chromatography, high speed molecular sieve chromatography and electrophoresis. Two or more of the above methods are generally suitably combines.
More specially, as the basic anion exchanger, there may be suitably used DEAE-Sephadex A-25 or A-50, DEAE-Sepharose CL-6B, DEAE Sephamil (manufactured by Pharmacia Inc.), or an anion exchanger containing a diethylamino group, aminoethyl group or a quarternary aminoethyl group. The buffer used for the chromatography is preferably Tris-HCI or phosphate buffer with a pH of 6.0-9.0. The antitumor polypeptide-containing culture liquid is diluted with such a buffer having a concentration of as low as 0.05 M to obtain a liquid having a salt concentration of 0.1 M or less. The liquid is then contacted with the anion exchanger to allow the polypeptide to be adsorbed thereon. The elution of the antitumor polypeptide may be carried out with a salt solution such as 0.1-0.2 M NaCI or KCI solution. The polypeptide is eluted at a salt concentration of near 0.2 M. The contact of the polypeptide with the anion exchanger is desirably conducted by a column method. In the case of a large scale treatment, however, a batch method may be adopted if desired. Before subjecting the anion exchange chromatography, the sample is preferably pretreated with the use of an ultrafiltration membrane for the removal of low molecular weight substances and for improving the purification efficiency.
The solution obtained by the anion exchange chromatography is, after dialysis, subjected to gel filtration using a filtration medium such as Sephadex G-75 or G-100 (manufactured by Pharmacia Inc.), Sephacryl S-200 (manufactured by Pharmacia Inc.), Biogel P-100 (manufactured by Biorad Ind.) or Toyo Pearl HW-50 or HW-55 (manufactured by Toya Soda Industry Co., Ltd.). The buffer used is preferably Tris-HCI or phosphate buffer having a pH of 6.0-9.0. To prevent adsorption, a salt such as NaCI may be desirably added in an amount of 0.2-0.5 M. This step generally provides 2-10 fold purification.
The antitumor polypeptide-containing solution obtained by the anion exchange chromatography may be purified by hydrophobic chromatography. In this case, Butyl Toyo Pearl 650 (manufactured by Toyo Soda Industry Co., Ltd.) etc. may be used as a medium and a salt such as ammonium sulfate or NaCI is used for the elution of the polypeptide. This step provides 5-30 fold purification and at least 80% recovery rate. The specific activity of the antitumor polypeptide after this step is 1x10⁶ or more and the content of the poiypeptide is 1.0% or more.
The polypeptide-containing solution purified by gel filtration is then subjected to a high performance anion exchange chromtography is a Pharmacia Fast Protein, Peptide, Polynucleotide Liquid Chromatography system using Mono Q HR5/5 column (a high performance anion exchange column manufactured by Pharmacia Inc.), thereby to obtain a purifed sample. This step provides 5-10 fold purification and 70-90% recovery of activity. The conditions under which the high performance anion exchange chromatography is performed are the same as those for the anion exchange chromatography described previously.
The antitumor polypeptide-containing solution purified by FPLC may be further purified to homogeneous active protein in the sense of SDS-electrophoresis by FPLC repeated again using mono Q HR5/5 column. By this treatment, 5-10 fold purification is attained and the specific activity is increased to 5x10_. units per mg-protein.
However, when the purified sample which is homogeneous and pure by the criteria of SDS- electrophoresis is subjected to ion chromatography in an FPLC system using Mono Q HR5/5 column under different elution conditions, three peaks of activity are found to be eluted. Each peak is purified again on FPLC using the same elution conditions to obtain three kinds of active protein samples named TNF-1, TNF-2 and TNF-3 (eluted in this order in the previous FPLC) whose physical and chemical properties and specific activity to L-929 cells are shown in the table below.
As seen from the above table, there is no difference between TNF-1, TNF-2 and TNF-3 with respect to molecular weight and isotropic point but they differ in specific activity. TNF-1, TNF-2 and TNF-3 have an N-terminal amino acid sequence shown below.
In the above N-terminal amino acid sequence, the fourth amino acid expressed as X is not identifiable by a vapor-phase amino acid sequence analyzer and is not serine. There is a possibility that X is cystein which is unable to be detected by this method. It is disclosed that the N-terminal amino acid sequence of the previously described TNF from human HL-60 cell line is
The amino acid sequence of TNF-1, TNF-2 and TNF-3 differ from that of TNF in that, in the former polypeptides, the fourth amino acid is not Ser, the fifth amino acid is Thr rather than Ser, and the tenth amino acid is Arg or Pro rather than Asp. Further, the twelfth amino acid of TNF-1 is Phe. Therefore, the antitumor Polypeptide according to the present invention apparently differs from known TNF obtained from the HL-60 cells in N-terminal amino acid sequence.
Japanese Published Unexamined Patent Application No. 60-19719 discloses that the N-terminal amino acid sequence of rabbit's TNF is;
His-Val
which differs from that of TNF of HL-60 in that the former lacks the two N-terminal amino acids and has different amino acids at the fourth, seventh, eighth and thirteenth positions. In the other, greater portion of the amino acid sequence, it says that there is no difference between TNF of rabbit and TNF of HL-60.
The antitumor polypeptide (a mixture of TNF-1, TNF-2, and TNF-3) according to the present invention which shows a single band in SDS polyacrylamide gel electrophoresis is digested with trypsin. Thus, 3.3u.g of trypsin is added to 100 µl of an aqueous solution containing 100 µg of the antitumor polypeptide and the mixture is allowed to stand at 37°C and pH 8.0 for 22 hours. The digest is applied to RP318 (column for reverse phase HPLC manufactured by Biorad Inc.) for HPLC to obtain eight fragments F-1 through F-8. Each fragment is subjected to Edman degradation using amino acid sequencing analyzer (Model 470A manufactured by Applied Biosystems Inc.) and the resulting liberated phenylthiohydantoin-amino acids are analyzed by HPLC (Shimadzu LC-4A type) to determine the amino acid sequence in the conven- tonal manner. The results are as follows.
Since any structure deduced from the results of anlysis of the tryptic fragments F-1 through F-8 is found in the structure of TNF of HL-60, it is believed that the amino acid sequence downstream of the thirteenth amino acid from the N-terminal of each of TNF-1, TNF-2 and TNF-3 is identical with that of TNF of HL-60.
The highly purified, antitumor polypeptide according to the present invention is expected to show no side effects when dosed to human bodies and to exhibit necrosis activity exclusively to tumor cells. The purified antitumor polypeptide shows no acute or subacute toxicity when intravenatically dosed to mouse. If, therefore, the polypeptide is intravenatically dosed to a terminal stage of cancer patient with metastatic lung carcinoma from kidney, the focus will dissapear, contract or stop enlarging. The antitumor polypeptide according to the present invention does not exhibit cytotoxicity against human normal cells WI-38 and Flow 1000 and fetal mouse cells, but gives cytotoxic activity against human tumor cells Hela and KB and mouse tumor cell sarcoma 180 and L-1210. Further the polypeptide exhibits excellent cytotoxity against T-24 cells which is known to be insensitive to conventional TNF[Science 230, 943-945 (1985)].
The following Examples will further illustrate the present invention.

Example 1

(1) Production of Antitumor Polypeptide by suspended culture of THP-1 cells:

Into a 300 I incubator 200 I of RPM-1640 sterile medium containing 5% fetal bovine serum was poured, into which was suspended THP-1 cells [Int. J. of Cancer 26, 171-176 (1980)] in an amount so that the cellular density became 2x10^* /ml. The cells in the suspension were incubated at 37°C for 4 days and the culture was subjected to centrifugation to collect THP-1 cells under sterile conditions. The cells were then added to 200 I of serum-free RPMI-1640 medium contained in another incubator, to which was mixed 100 ng/mi of TPA. The mixture was incubated under sterile conditions at 37°C for 5 days with gentle stirring (100 r.p.m.) for induction. The culture was subjected to centrifugation for the separation and removal of the cells, thereby to ootain a supernatant liquid having antitumor polypeptide activity of 1.5x1 03 units/ml. The supernatant was concentrated to 1/10 volume by means of ultrafiltration membrane (HVLP OHV20 manufactured by Millipore Inc.). Solid ammonium sulfate - (65% of the saturated amount) was dissolved in the concentrate to precipitate proteins. The precipitate was separated by centrifuge (1000 r.p.m., 20 min.) and dissolved in a small amount of 0.05 M Tris-HCI buffer (pH 7.7) followed by dialysis against the same buffer at 5°C for 24 hours. After addition of equivolume of the preceeding buffer, the protein liquid was applied to DEAE-Toyo Pearl M650 column (5x40 cm) which was previously equilibrated with the same buffer. The column was washed with 1.0 I of the buffer and eluted with the same buffer containing 0.2 M NaCI.
Fractions (2.0 I) having antitumor polypeptide activity were pooled and subjected to ammonium sulfate fractionation (40-55% saturated fraction). The thus obtained precipitate was dissolved in a small amount of water and dialyzed against the preceding buffer at 5°C for 24 hours. The dialysis inner liquid was added with ammonium sulfate - (40% of the saturated amount) and the solution was centrifuged for the removal of insoluble matters and subjected to hydrophobic chromatography using Butyl-Toyo Pearl 650X column (2.5 x 30 cm), previously equilibrated with 0.05 M Tris-HCI buffer containing ammonium sulfate (40% of the saturated amount), at an elution rate of 2.0 ml/min, thereby to collect a fraction having antitumor polypeptide activity. This was dyalyzed against 0.05 M Tris-HCI buffer (pH 7.8). The inner liquid of the dialysis was injected on Mono Q HR5/5 column (High Performance anion exchange column) which was previously equilibrated with 50 mM Tris-HCI buffer (pH 8.5). After washing with the same buffer, the column was eluted with stepwisely increased gradients of NaCl solutions (0.1, 0.15, 0.2 and 0.3 M). The antitumor polypeptide activity was eluted with 0.2 M NaCI. The eluate was then purified until a specific activity of 1x10^* units/mg-protein was reached. This step provided 5-15 fold purification and at least 80% recovery.
The active fractions were combined and treated again with Pharmacia FPLC.(Fast Protein, Peptide, Polynucleotide Liquid Chromatography) system using Mono Q HR5/5 column under the same conditions as above. The elution pattern in the second FPLC is shown in Fig. 1 in which the ordinate represents absorbance (%) at 280 nm and abscissa represents the elution time (min). As seen from Fig. 1. the antitumor peptide activity is eluted with 0.1 M NaCI and is in good conformity with the peak monitored by absorbance at 280 nm. The active fractions were pooled and dialyzed against pure water and then lyophilized to obtain 200 µg of a purified sample having a specific activity of 5.0x10. units/mg-protein.
The protein sample was subjected to anion exchange column Mono Q chromatography under the conditions shown in Table 1.
Three peaks were eluted at retention time of 35, 36 and 37.8 minutes and the corresponding fractions were collected separately and named TNF-1, TNF-2 and TNF-3, respectively. Each fraction was again subjected to chromatography in the same manner as above to obtain purified protein sample which was homogeneous in the following criteria.

(2) Characterization of Antitumor Polypeptide:

Each protein sample was subjected to reverse phase FPLC using Pro-FPC HR5/2 column (C-4 reverse phase medium manufactured by Pharmacia Inc.) using 0.1% trifluoroacetic acid as a developer with a linear gradient of 0-70% acetonitrile concentration. The elution pattern for TNF-1 is shown in Fig. 2. The TNF-1 polypeptide was eluted at an acetonitrile concentration of about 36%. No other protein peaks were detected. Similar results were obtained with respect to TNF-2 and TNF-3. Thus, each of TNF-1, TNF-2 and TNF-3 is regarded as being a single substance in the sense of the reverse phase FPLC.
Next, each protein sample is subjected to SDS- polyacryl-amide gel electrophoresis (SDS-PAGE). Thus, the sample was applied to 15.0% polyacrylamide gel containing 0.1% SDS and electrophoresed using a slub electrophoresis apparatus (Protean, 16 cm, manufactured by Biorad Inc.) at a constant current of 20 mA. The protein was detected by silver staining. In any of TNF-1, TNF-2 and TNF-3 a single band was detected at a location of 17.4 kd. No other bands were detected. It is therefore revealed that each of the samples TNF-1, TNF-2 and TNF-3 is homogeneous in the sense of the SDS-PAGE electrophoresis.
Each sample was subjected to ioelectric focusing gel electrophoresis using Ampholine polyacrylamide gel (manufactured by LKB Inc.) for the measurement of isoelectric point (pl). Each sample was found to have an isoelectric point of 5.7
Each sample (ca. 10 ug) was further subjected to amino acid sequence analysis using Amino Acid Sequencing Analyzer Model 470A (manufactured by Applied Biosystems Inc.).The N-terminal amino acid sequences of the samples were determined as follows:
In the above N-terminal amino acid sequence, the fourth amino acid expressed as X is not identifiable by a vapor phase amino acid sequence analyzer and is not serine. There is a posibility that X is cystein which is unable to be detected by this method..
The antitumor polypeptide (a mixture of TNF-1, TNF-2 and TNF-3) according to the present invention which shows a single band in SDS polyacrylamide gel electrophoresis was digested with trypsin. Thus, 3.3 µg of trysin was added to 100 µl of an aqueous solution containing 100 µg of the antitumor polypeptide and the mixture was allowed to stand at 37°C and pH 8.0 for 22 hours. The digest was applied to RP318 column - (manufactured by Biorad Inc. column for reverse phase HPLC) for HLPC to obtain eight fragments F-1 through F-8. Each fragment was subjected to Edman degradation using amino acid sequencing analyzer Model 470A (manufactured by Applied Biosystems Inc.) and the resulting liberated phenylthiohyndantoin-amino acids were analyzed by HPLC (Shimadzu LC-4A type) to determine the amino acid sequence in the conventional manner. The results are as follows:

Experimental Example 1

T24 cells were suspended in MEM-medium supplemented by 10 w/w% FCS and seeded in a Limbro 96 well microfilter plate in an amount of 1 x 10⁴/200 µl/well and cultured at 37°C for 48 hours in the presence of 0.5% CO₂. Thereafter, the supernatant of THP-1 culture product 1% of purity, 5x10^Sunits/ml, was added in amounts of 10,000 units/ml, 1,000 units/ml, 100 units/ml and 0 units/ml respectively to the medium containing 0.1 µg/ml of actinomycine D and the culture was continued at 37°C for 16 hours in the presence of 0.5% CO_z. Then, 10µCi/ml of ³H-thymidine was added to respective culture mixtures. After 8 hour culture, ³H-thymidine taken into the cells was counted by a liquid scintillation counter for the determination of the antitumor activity. The less the taken-up amount is the higher the antitumor activity is. The results are shown in Table 9. The respective value is an average of four experimental values. The value in parentheses show the rate to the amount of when only actinomycin D was dosed and THP-1 culture product was not dosed.
THP-1 cells used in the invention was described in "Int. J. Cancer 26, p.171-176(1980)". The present inventors have accomplished the invention with the cells released from the author of the paper. The cells were also described in "Proc. Nati. Acad. Sci., U.S.A. 80, 5397-5401(1983)" and "Cancer Research 42, 484-489(1982)"[It says that the cells were got from Dr. Rovera]. The experts are easy to obtain the cell and the present inventors will give the cells to any experts.
As will be appreciated from the foregoing, the novel antitumor polypeptide according to the present invention obtained by suspended-culture of THP-1 cells does not exhibit cytotoxicity to human normal cells but gives cytotoxicity to human tumor cells. The antitumor polypeptide may be prepared by a non-expensive serum-free medium. The novel DNA synthesized by a method according to the present invention can express novel antitumor polypeptides which show no cytotoxicity to normal cells but exhibit cytotoxicity to human tumor cells. Some of the novel antitumor polypeptides exhibit cytotoxicity to T-24 cells, which are insensitsive to conven- tonal TNF, and against primary culture cells which are obtained from metastasis focus of a patient with rhabdomyo sarcoma from Mullerrian duct and which show resistance to any anti-tumor chemotra agent.

Claims

1. An antitumor polypeptide containing a peptide fraction having the following N-terminal amino acid sequence: Val-A-Ser-X-Thr-B-Thr-C-D-E-F-G-Val-Ala-His-Val-AJa-Asn wherein A represents Arg or Lys, B represents Arg or Pro, C represents Arg or Pro, D represents Ser or Lys, E represents Arg or Pro, F represents Lys or Val, G represents Phe or Pro and X is an unidentified amino acid, and tryptic peptide fragments of

and having the following physical and chemical properties:

(a) molecular weight : 17400+500 (SDS electrophoresis);

(b) isoelectric point: pl 5.7+0.2 (gel isoelectric point electrophoresis);

(c) pH stability: stable at pH in the range of 6-9;

(d) temperature stability: activity is lost by about 60-70% when heated at 65°C, pH 7.0 for 1 hour;

(e) stability to protease: inactivated;

(f) physiological activity: shows no cytotoxicity against human normal cells but exhibits cytotoxicity to human tumor cells.

2. A method of preparing the following antitumor polypeptide which comprises culturing human myeolocytic leukemia cells THP-1 under or after contacting with a differenciation inducing agent;

The antitumor polypeptide containing a peptide fraction having the following N-terminal amino acid sequence: Val-A-Ser-X-Thr-B-Thr-C-D-E-F-G-Val-Ala-His-Val-Ala-Asn wherein A represents Arg or Lys, B represents Arg or Pro. C represents Arg or Pro, D represents Ser or Lys. E represents Arg or Pro, F represents Lys or Val, G represents Phe or Pro and X is an unidentified amino acid, and tryptic peptide fragments of

and having the following physical and chemical properties:

(a) molecular weight : 17400+500 (SDS electrophoresis);

(b) isoelectric point: pl 5.7+0.2 (gel isoelectric point electrophoresis);

(c) pH stability: stable at pH in the range of 6-9;

(d) temperature stability: activity is lost by about 60-70% when heated at 65°C, pH 7.0 for 1 hour:

(e) stability to protease: inactivated;

(f) physiological activity: shows no cytotoxicity against human normal cells but exhibits cytotoxicity against human tumor cells.

3. A method as claimed in claim 2 wherein culturing is suspended culturing.

4. A method as claimed in claim 2 wherein the differential inducing agent is a substance capable of inducing malignant monocyte cells into macrophages, massive monocyte cells.

5. A method as claimed in claim 4 wherein the differentiation inducing -agent is one or more selected from the group consisting hemin, actionomycin D, hexamethylene aclacino mycin A, Teleocidin, mitomycin C, Bleomycin, propionic acid, sodium acetate, cadaverine, Tunicamycin, 12-o-tetradecanoylphrbol-13-acetate (TPA), lym- phokyte such as -y-interferon, D-factor, arginase, histone HI, lipopolysaccharide (LPS), lipid A, glucocorticoid, Id-25-dehydrooxyvitamin D₃, poly - (I), poly(ADP-ribose), BCG and chloroquine.